Structural isomerism of colloidal semiconductor nanocrystals has been largely unexplored. Here, we report one pair of structural isomers identified for colloidal nanocrystals which exhibit thermally-induced reversible transformations behaving like molecular isomerization. The two isomers are CdS magic-size clusters with sharp absorption peaks at 311 and 322 nm. They have identical cluster masses, but slightly different structures. Furthermore, their interconversions follow first-order unimolecular reaction kinetics. We anticipate that such isomeric kinetics are applicable to a variety of small-size functional nanomaterials, and that the methodology developed for our kinetic study will be helpful to investigate and exploit solid–solid transformations in other semiconductor nanocrystals. The findings on structural isomerism should stimulate attention toward advanced design and synthesis of functional nanomaterials enabled by structural transformations.

Prussian blue analogs with an open framework are ideal cathodes for Na‐ion batteries. A superior high‐rate and highly stable monoclinic nickel hexacyanoferrate (NiHCF‐3) is synthesized via a facile one‐step crystallization‐controlled co‐precipitation method. It gives a high specific capacity of 85.7 mAh g−1, nearly to its theoretical value. It also exhibits an excellent rate capability with a high capacity retention ratio of 78% at 50 C and a stable cycling performance over 1200 cycles. Through the ex situ X‐ray diffraction and pair distribution function measurements, it is found that the monoclinic structure with distorted framework is greatly related to the high Na content. The electronic structure studies by density functional theory (DFT) calculation demonstrate that NiHCF‐3 deformation promotes the framework conductivity and improves the electrochemical activity of Fe, which results in an ultrahigh‐rate performance of monoclinic phase. Furthermore, the high‐quality monoclinic (NiHCF‐3) exhibits excellent compatibility with both hard carbon and NaTi2(PO4)3 anodes in full cells, which shows great prospects for the application in the large‐scale energy storage systems.

LiCoO2 is used as a cathode material for lithium‐ion batteries, however, cationic/anodic‐redox‐induced unstable phase transitions, oxygen escape, and side reactions with electrolytes always occur when charging LiCoO2 to voltages higher than 4.35 V, resulting in severe capacity fade. Reported here is Mg‐pillared LiCoO2. Dopant Mg ions, serving as pillars in the Li‐slab of LiCoO2, prevent slab sliding in a delithiated state, thereby suppressing unfavorable phase transitions. Moreover, the resulting Li‐Mg mixing structure at the surface of Mg‐pillared LiCoO2 is beneficial for eliminating the cathode‐electrolyte interphase overgrowth and phase transformation in the close‐to‐surface region. Mg‐pillared LiCoO2 exhibits a high capacity of 204 mAh g−1 at 0.2 C and an enhanced capacity retention of 84 % at 1.0 C over 100 cycles within the voltage window of 3.0–4.6 V. In contrast, pristine LiCoO2 has a capacity retention of 14 % within the same voltage window.

Hard carbon (HC) is one of the most promising anode materials for sodium-ion batteries (SIBs) due to its suitable potential and high reversible capacity. At the same time, the correlation between carbon local structure and sodium-ion storage behavior is not clearly understood. In this paper, the two series of HC materials with perfect spherical morphology and tailored microstructures were designed and successfully produced using resorcinol formaldehyde (RF) resin as precursor. Via hydrothermal self-assembly and controlled pyrolysis, RF is a flexible precursor for high-purity carbon with a wide range of local-structure variation. Using these processes, one series of five representative RF-based HC nanospheres with varying degrees of graphitization were obtained from an RF precursor at different carbonization temperatures. The other series of HC materials with various microscopic carbon layer lengths and shapes was achieved by carbonizing five RF precursors with different cross-linking degrees at a single carbonization condition (1300 °C and 2 h). On the basis of the microstructures, unique electrochemical characteristics, and atomic pair distribution function (PDF) analyses, we proposed a new model of “three-phase” structural for HC materials and found triregion Na-ion storage behavior: chemi-/physisorption, intercalation between carbon layers, and pore-filling, derived from the HC phases, respectively. These results enable new understanding and insight into the sodium storage mechanism in HC materials and improve the potential for carbon-based SIB anodes.

For reaching a high-performance of electrode materials, it is generally believed that understanding the structure evolution and heterogeneous alignment effect is the key. Presently, a very simple and universal applicable...